1. Field of the Invention
The invention relates to an X-ray examination apparatus which is provided with an X-ray detector which includes an image sensor arranged to derive an image signal and a measurement signal from the X-ray image, and also provided with an exposure control for adjusting the X-ray examination apparatus on the basis of the measurement signal.
2. Description of Related Art
An X-ray examination apparatus of this kind is known from German Offenlegungsschrift DE 44 06 677.
The known X-ray examination apparatus includes an X-ray detector with a conversion screen and an image sensor. The conversion screen derives an optical image from the X-ray image and the image sensor derives the image signal from the optical image. The image sensor of the known X-ray examination apparatus is provided with shift registers for reading out electrical charges from the image sensor. The shift registers, moreover, are sensitive to light of the optical image and convert a part of the light of the optical image into electrical charges which constitute the measurement component.
The shift registers are arranged at the edge of the image sensor. Consequently, it is a drawback of the known X-ray examination apparatus that the measurement component can be derived only from a part of the edge of the optical image. Because brightness values of the edge of the optical image usually are not representative of brightness values in the remainder of the optical image, the measurement signal is not very well suitable for accurate adjustment of the X-ray examination apparatus in order to form an image signal whereby details in the optical image can be suitably visualized.